Dinuclear bridged copper and palladium complexes



United States Patent Office U.S. Cl. 260429 5 Claims ABSTRACT OF THE DISCLOSURE Dinuclear bridged transition metal complexes in which the transition metals are different and are selected from Groups VI-A, VII-A, VIII and I-B of the Periodic Table and in which the bridging ligands are selected from acetate propionate, and benzoate.

This is a division of an application, Ser. No. 572,221, filed Aug. 15, 1966.

This invention relates to dinuclear bridged transition metal complexes, a process for their preparation and to their use as catalysts.

Dinuclear bridged transition metal complexes are known in which the two transition metals are the same. We have found that certain compounds of this general kind-can be made in which the transition metal atoms are diiferent.

Accordingly the present invention provides dinuclear bridged transition metal complexes in which the transition metal atoms are different and are selected from Groups VLA, VII-A, VIII and I-B of the Periodic Table of the Elements, and in which the bridging ligands are univalent and do not incorporate chelating ligands.

The Periodic Table of the Elements referred to is that given in Advanced Inorganic Chemistry by Cotton and Wilkinson published by Interscience (1962).

By chelating ligand we mean a bi-dentate ligand which is attached at two sites to the same metal atom. The bridging ligands may be bi-dentate but, if so, must be attached to one site of each metal atom.

For ease of understanding, examples of the compounds of the present invention may be regarded as containing a group represented by the following formula:

where L, L are univalent non-chelating bridging ligands which maybe the same or different and M', M are transition metals as defined above; but the present invention does not depend on the structural accuracy of this representation nor of any of the other formulae given herein. Complexes according to our invention may contain one or more bridging ligands and may contain metal-metal bonds in addition to the aforesaid bridging ligand of ligands.

Examples of transition metals are platinum, palladium, tungsten, chromium, molybdenum, iron and copper. Examples of ligands L and L are chloride, bromide, sulphide, thiocyanate, acetate, propionate, benzoate, phosphido or groups containing selenium, arsenic or antimony.

In addition to the group represented by Formula I above the compounds of the present invention will contain other ligands as required to satisfy the coordination numbers and valencies of the transition metal atoms present.

3,453,299 Patented July 1, 1969 These ligands may include neutral and monovalent ligands and may be the same or different to the extent permitted by the co-ordination requirements of the transition metal atoms.

Many of the compounds of the present invention may be obtained in cis or trans forms depending upon the method of preparation and both of these and other isomeric variations are to be included within the scope of the present invention.

According to a further aspect of the invention we provide a process for the preparation of the compounds provided by the present invention which comprises reacting a compound or complex of one transition metal with a compound or complex of a second transition metal with or without additional ligand-forming reactants, the transition metals being selected from Groups VI-A, VII-A, VIII and LB of the Periodic Table.

For example, a complex of one transition metal containing halide and substituted phosphine ligands may be reacted with a halogen-containing compound of the second transition metal. Alternatively, the carbonyls of two different transition metals may be reacted with an organic phosphine to form a phosphido bridged dinuclear carbonyl. The organic phosphine may be a monophosphine, such as diphenyl phosphine, or a diphosphine, such as tetra methyldiphosphine. As a further example, two different metal salts of a single organic acid may be reacted with the same free organic acid which forms bridging ligands.

The dinuclear bridged transition metal complex produced by the aforementioned process may be reacted with further reagents to bring about ligand exchange, For example, ,u,;t'-dihaloplatinum palladium complexes may be treated with diphenylphosphine, so that the halogen bridges are replaced with diphenylphosphido bridges. Also, non-bridging ligands may be replaced by such means.

Reaction conditions will vary according to the nature of the starting materials, reagents and product, but in many cases it is convenient to perform the reaction in an inert solvent. An inert atmosphere and elevated temperatures and pressures may also be used.

The compounds of the present invention are useful as catalysts in a variety of organic reactions, for example hydrogenation, carbonylation and oxidation.

It is to be understood however, that not all compounds are suitable as catalysts in all types of oragnic reaction: suitability should be determined by a small-scale trial in each case. The compounds containing platinum and palladium are particularly useful as catalysts for carbonylation reactions, as disclosed in our copending British patent application 39,723/65, and also for hydrogenation of unsaturated organic compounds, for example alkynes, alkenes and mixtures of same. The hydrogenation reactions are preferably carried out at elevated pressure and temperature.

The invention is illustrated by, but not limited to the following examples, in which all parts are by weight, unless otherwise stated.

EXAMPLE 1 Dichlorobis (tri n butylphosphine) ,u., 1.' dichloroplatinum palladium [(nBu P) C1 PtPd] was prepared as follows. Trans-bis (tri-n-butylphosphine) dichloroplatinum (1 part) was dissolved in ethyl alcohol 40 parts and added to sodium chloropalladite (0.56 part) also dissolved in ethyl alcohol (40 parts). The solution was refluxed under nitrogen for 1 hour. The resulting mixture was filtered, concentrated, water added and then extracted with benzene. The product (1.1 parts) obtained from the benzene layer was recrystallized from petroleum ether (B.Pt. 60-80 C.) containing a small amount of benzene M.Pt. -7 C.

3 Analysis.Calculated for C H Cl P PtPd: C, 34.0%; H, 6.37%; Cl, 16.75%. Found: C, 34.36%, 33.97%; H, 6.52%, 6.59%; Cl, 16.55%, consistent with the formula:

Pt Pd The product was believed to be the trans isomer from dipole measurments.

EXAMPLE 2 The same product as in Example 1 was obtained when cisor trans-bis (trim-butylphosphine)dichloroplatinum (1 part) was mixed with palladium chloride (0.27 part) and the resulting dry mixture heated at 170l80 C., under an atmosphere of nitrogen, for two hours. The product was isolated by extracting with benzene and isolating as above.

EXAMPLE 3 The procedure of Example 1 was repeated using transbis (trim-butylphosphine)dibromoplatinum and sodium bromopalladite.

The product analysis was consistent with the formula BuaP Br Br 7 Br Br IBu;

The recrystallized product had a melting point of 144- 6 C.

EXAMPLE 4 Dichlorobis(tri n butylphosphine) ;/.,,u.' bis(diphenylphosphido) platinum palladium was prepared as follows. Dichlorobis(tri n butylphosphine) t dichloroplatinum palladium (1.0 part), prepared as in Example 1, was dissolved in ethanol (40 parts) under nitrogen. Diphenylphosphine (0.50 part) was added to the solution and the resulting mixture stirred at room temperature for 1 hour. After this time sodium ethoxide (prepared from 0.058 part of sodium) was added when a color change from pale orange to dark red occurred. Nearly all the ethanol was evaporated off under reduced pressure and then water and benzene were added. The benzene layer was separated, dried with magnesium sulphate, concentrated to small bulk and passed down an alumina column made up in the same solvent. On eluting with benzene, a yellow band was collected from which the product (0.34 part) was isolated by removal of the solvent and recrystallization from petroleum ether (B.Pt. 6080 C.) containing a small amount of methylene dichloride.

Analysis.Calculated for C H P Cl PdPt: C, 50.25%; H, 6.46%, 10.81%; Cl, 6.19%. Found: C, 50.93%; H, 6.67%; P, 11.20%; Cl, 6.55%.

This is consistent with the formula:

P112 Cl\ P Pt Pha EXAMPLE 5 P (n-B 11):: i/

.4 organic layer was recrystallized from ethyl aclohol M.Pt. 184-188 C.

Analysis. Calculated for C H Cl P PtPd: C, 28.30%; H, 5.50%; Cl, 18.58%; P, 8.12%. Found: C, 28.62%; H, 5.72%; Cl, 18.79%; P, 8.6%, consistent with the formula:

The product was believed to be the trans isomer from dipole measurements.

EXAMPLE 6 Tetra -acetatocopper (II) palladium (H) was prepared as follows. Palladous acetate (4.5 parts) and cupric acetate monohydrate (4 parts) were refluxed in analytical grade acetic acid for 15 minutes. The green solution obtained was filtered and left to stand for 14 days. Dark brown crystals were slowly deposited. (Yield 3.1 parts.) The crystals retained their form in the presence of acetic acid vapour but prolonged drying or ether washing caused them to degenerate to a green powder, decomposing at 178 C. Analysis indicated the presence of 15.6% copper and 26.2% palladium. The calculated metal content for C H CuO Pd is 15.6% Cu and 26.2% Pd.

An X-ray photograph of the green powder showed no separate palladous acetate or cupric acetate phases. Other physical measurements, including electron spin resonance, infra-red and ultraviolet/visible spectroscopy, and molecular weight determination indicate a probable structure for the compound-- l CH3 CH3 EXAMPLE 7 The procedure of Example 6 was repeated using palladous benzoate and cupric benzoate, first in benzene and then in acetone solution. Again, no crystalline compounds were isolated, but physical evidence for the presence of analogous bridged compounds was obtained by means of electron spin resonance and ultraviolet/visible spectroscopy.

EXAMPLE 9 Chromium hexacarbonyl (1.85 parts), molybdenum hexacarbonyl (2.15 parts), tetramethyldiphosphine (1.02 parts) and benzene (6.2 parts) were heated in a sealed tube at 260 C. for 46 hours under nitrogen. The solvent was removed under reduced pressure and the residue purified by chromatography on alumina. Elution with 20% benzene in petroleum ether, evaporation of the eluate from the orange band, and recrystallization of the residue (benzene/petroleum ether) aflorded the product (1.54 parts 37% yield) as orange cubes, identified by elemental analysis and infra-red and nuclear magnetic resonance spectra, was J-(dimethylphosphido) (tetracarbonylchromium) (tetracarbonylmolybdenum) of formula:

Diphenylchlorophosphine chromium pentacarbonyl (0.5 part) and diphenylphosphineiron tetracarbonyl (0.4 part) were refluxed in tetrahydrofuran (22 parts) for 60 minutes to given a brownish-red solution. The solvent was removed under reduced pressure and the residue extracted with hexane. The resulting solution was characterized spectrographically. The ultra-violet/visible spectrum exhibited A max. at 223 my and inflections at 330 and 348 m The solid product recovered from the solution was unstable, but the spectrum of the solution was consistent with the two possible structures:

Phg P I! (OC) MoPPh PPh Fe(C0)4 (OC) Mo\----Fe(CO)3 P7 Phz EXAMPLE 12 Diphenylchlorophosphine tungsten pentacarbonyl 0.5 part) and diphenylphosphine iron tetracarbonyl (Fe(CO) PPh H; 0.3 part) were refluxed in tetrahydrd furan (22 parts) for 70 minutes to give a deep brownishyellow solution. The solvent was removed under reduced pressure and the residue extracted with hexane. The resulting solution was characterized spectrographically. The ultra-violet/ visible spectrum exhibited A max. at 222 my and inflections at 300 and 335 mg. The solid product recovered from the solution was unstable, but the spectrum of the solution was consistent with the two possible structures:

6 EXAMPLE 13 Dichlorobis(tri n butylphosphine) ,uJt' dichloroplatinum palladium (0.42 part) was dissoved in benzene (175 parts). 1 part (by volume) of this solution was added to 50 parts (by volume) of benzene containing 10% by weight of each of n-hexyne-l and n-octene-l. The mixture was transferred to an autoclave vessel which was pressured up to atmospheres with hydrogen and heated up to 175 C., when a pressure of atmospheres was obtained. After 1 hour without agitation under these conditions, the vessel was cooled, vented and the reaction products were analysed by gas chromatography.

Each result is the duplicate of two tests. Product analysis (percent by Weight). n-Hexane 1.8 n-Hexene-l 7.2 n-Hexyne-l (unreacted, by difference) 1.0

Total n-C 10.0

n-Octane 0.9 n-Cctene-l (unreacted, by difference) 9.1

Total C 10.0 Benzene 80.0 EXAMPLE 14 The procedure of Example 13 was repeated, using 0.51 part of dibromobis(tri-n-butyl phosphine)-;t,;t-dibromoplatinum palladium. Product analysis (percent by weight).

n-Hexane 1.6 n-Hexene-l 5.8 n-Hexyne-l (unreacted, by difference) 2.6

Total n-C 10.0

n-Octane 0.8 n-Octene-l (unreacted, by difference) 9.2

Total n-C 10.0 Benzene 80.0

EXAMPLE 15 The procedure of Example 13 was repeated using 0.38 part of dichlorobis(tri-n-propylphosphine)-,u., t'-dichloroplatinum palladium. Product analysis (percent by weight).

n-Hexane 1.7 n-Hexene-l 8.2 n-Hexyne-l (unreacted, by difference) 0.1

Total n-C 10.0

n-Octane 0.8 n-Octane-l (unreacted, py difference) 9.2

Total n-C 10.0 Benzene 80.0

EXAMPLE 16 The procedure of Example 13 was repeated using 0.46 part of dichlorobis(tri-n-butylphosphine) uad-bis (diphenylphosphido) platinum palladium. Product analysis (percent by weight).

What is claimed is:-

1. Dinuclear bridged transition metal complexes in which the transition metals are different and are selected from copper and palladium and in which the bridging ligands are selected from the group consisting of acetate, propionate and benzoate.

2. Tetra ,a-acetatocopper palladium as a new compound.

3. Tetra ,a-propionatocopper palladium as a new compound.

4. Tetra a-benzoatocopper palladium as a new compound.

5. A process for preparing dinuclear bridged transition metal complexes in which the transition metals are different which comprises reacting (1) a salt of one transition metal and an organic acid, (2) a salt of a second transition metal and the same organic acid with (3) said organic acid, said transition metal being selected from copper and palladium.

- References Cited UNITED STATES PATENTS 2,850,528 7/1958 Closson 260438.1 XR 2,918,494 12/1959 Closson et al. 260438.1 XR 5 3,247,262 4/1966 Kaeding 260438.1 XR

OTHER REFERENCES Dwyer et al.: Chelating Agents and Metal Chelates,

10 Academic Press, Inc., New York (1964), pp. 96-97.

Tsuchida et al.: Nature, vol. 178, pp. 1192-93 (1956).

US. Cl. X.R. 20 252 431; 260430, 438.1, 438.5, 439, 683.9, 690

McKeon et al. 260438.1 

